1. Field of the Invention
The present invention relates to an In-Plane Switching mode LCD (IPS-LCD) and, more particularly, to an electrode array structure of an IPS-LCD for obtaining a smooth curve in the dark region of the Voltage-Transparency (V-T) diagram.
2. Description of the Related Art
In-plane switching mode LCD (IPS-LCD) has developed for improving the view angle of a conventional twisted nematic LCD (TN-LCD). In an in-plane switching mode LCD (IPS-LCD), common electrodes and pixel electrodes are formed on a lower glass substrate (TFT substrate) and an in-plane electric field therebetween is generated to rearrange the liquid crystal molecules along the in-plane electric field. Accordingly, the IPS-LCD has been used or suggested for improving viewing angle, contrast ratio and color shift.
Depending on designs of the electrode array structure, the IPS-LCD is classified as a single-domain type and a two-domain type. FIG. 1 is a top view showing an electrode array structure of a single-domain IPS-LCD device 10 according to the prior art. In the IPS-LCD device 10, two adjacent gate lines 2 and two adjacent data lines 4 are arranged to form an approximately rectangular-shaped pixel area, in which a TFT structure 5, a comb-shaped pixel electrode 6, and a comb-shaped common electrode 8 are disposed. The center wiring portion 8I of the common electrode 8 transversely extends to across the pixel area. The teeth 6a of the pixel electrode 6 are disposed in the intervals between the teeth 8a of the common electrode 8. When an outer voltage is applied to the IPS-LCD 10, an in-plane electric field is generated between the adjacent teeth 6a and 8a. Also, each of the teeth 6a and 8a is formed as a strip profile and in parallel to each other, thus the distribution of the electric field generated therebetween is uniform and the liquid crystal molecules can be uniformly driven at the same time. However, this needs a high driving voltage.
For improving color shift of the single-domain IPS-LCD device 10, a two-domain IPS-LCD device 20 is developed as shown in FIG. 2. In the two-domain IPS-LCD device 20, two adjacent gate lines 12 and data lines 14 are arranged in a matrix form to define a pixel area 11, in which a TFT structure 15, a comb-shaped pixel electrode 16 and a herringbone-shaped common electrode 18 are disposed. Using the center wiring portion 18a of the common electrode 18 as the discrimination, the pixel area 11 is divided into a first sub-pixel area 11a and a second sub-pixel area 11b. In the first sub-pixel area 11a, the first teeth 16a of the pixel electrode 16 and the first bones 18a of the common electrode 18 are aligned from the lower left toward the upper right. In the second sub-pixel area 11b, the second teeth 16a and the second bones 18a are aligned from the upper left toward the lower right. When an external voltage is applied to the IPS-LCD device 20, the liquid crystal molecules positioned in different sub-pixel areas 11a and 11b respectively rotate in counterclockwise direction and in clockwise direction.
In addition, a multi-domain IPS-LCD device 20xe2x80x2 is developed as shown in FIG. 3. The tooth of the pixel electrode 16 is formed as a continuous saw-toothed profile extending along lengthwise direction, and the bone of the common electrode 18 is formed as a continuous saw-toothed profile extending along lengthwise direction. For example, as to the pixel electrode 16, the first tooth 16a in the first sub-pixel area 11a is parallel to the third tooth 16c in the second sub-pixel area 11b, and the inclination of the teeth 16a and 16c is xcex8. Similarly, the second tooth 16b and the fourth tooth 16c are in parallel to each other. As to the common electrode 18, the first bone 18a in the first sub-pixel area 11a is parallel to the third bone 18c in the second sub-pixel area 11b, and the inclination of the bones 18a and 18c is xcex8. Similarly, the second bone 18b and the fourth bone 18c are in parallel to each other. However, in the electrode array structure of the IPS-LCD device 20xe2x80x2, a steep curve is found in the dark region of a Voltage-Transparency (V-T) diagram. This is difficult to subdivide the gray scale.
The present invention provides an electrode array structure of a multi-domain IPS-LCD to solve afore-mentioned problems.
In in-plane switching mode LCD (IPS-LCD) device, each pixel area of an has at least two common electrodes extending along Y-axis direction and at least a pixel electrode extending along Y-axis direction, in which the pixel electrode is disposed between the two adjacent common electrodes in parallel. The common electrode and the pixel electrode have the same profile that is connected by a first strip-shaped segment, a second strip-shaped segment, a third strip-shaped segment and a fourth strip-shaped segment in sequence. The first segment is not parallel to the second segment, the first segment is not parallel to the third segment, the second segment is not parallel to the fourth segment, and the third segment is not parallel to the fourth segment.
Accordingly, it is a principal object of the invention to provide an electrode array structure to achieve a multi-domain IPS-LCD.
It is another object of the invention to provide the common electrode and the pixel electrode with the continuous saw-toothed profile.
Yet another object of the invention is to provide the common electrode formed by connecting four segments that are not parallel to each other.
It is a further object of the invention to obtain a smooth-tending curve in the dark region of V-T diagram.